Female sex workers (FSWs) are at heightened risk for acquiring and transmitting HIV infection because of biological, behavioral and structural risk factors. In Kenya's Coast Province, the site of the proposed study and a hotspot for sex work, sex workers and clients accounted for 18.2% of new HIV infections, and men who have sex with men, including those who sell sex (MSW), for 20.5%. These data suggest that most current HIV prevention initiatives for these most-at-risk populations are inadequate. Few HIV prevention interventions have addressed comprehensively the intersecting social worlds of sex workers, clients, and settings in which sex is transacted. The majority of venue-based interventions for SWs worldwide have been implemented in brothels, or other sex work-specific establishments. Few have been conducted in bars/clubs, have targeted clients and MSWs, and have been conducted in Africa. Therefore, we plan to develop and pilot a multi-level intervention in nightclubs/bars in Mombasa, Kenya. We will use a randomized controlled design to evaluate intervention feasibility via independent pre- and post-intervention cross-sectional surveys with 160 FSWs, 160 MSWs and 160 male clients, and cohorts of 80 FSWs, 80 MSWs and 80 male clients recruited from 2 intervention and 2 control bars/nightclubs venues. The specific aims of this mixed-methods study are to (1) understand the socio-cultural context of risk behavior, beliefs/understandings of HIV and risk; barriers to and facilitators of risk-reduction; and responses to intervention messages among 25 male clients, 25 MSWs, and 25 FSWs via formative research to inform intervention content to be refined in Phase 2 (Phase 1); (2) in collaboration with local key informants, design a multi-level risk-reduction intervention tailored o the local context and informed by theory and our prior work, that includes peer-delivered individual and group education, distribution of male and female condoms and lubricants, street theater presentations, on-site moonlight HIV testing and counseling and STI care, and manager meetings in Mombasa bars and nightclubs (Phase 2); (3) test the intervention package developed in Phase 2 for feasibility, acceptability, as well as participant level of exposure and intervention contamination at control sites via process measures; and (4) test the feasibility of an intervention evaluation design (in Phase 3) to be used in a future study, by: (a) developing and evaluating recruitment and data collection procedures; (b) determining the usefulness of potential biomarkers of condom use; (c) assessing retention of a longitudinal cohort of FSW, MSW, and clients; (d) developing power and sample size calculations to inform feasibility for a future venue-based combination prevention trial; and (e) comparing different ways of measuring condom use: self-report via interview and text messaging, and biomarkers among SWs so as to determine most relevant measures for use in a larger trial.